1. Field of the Invention
The invention relates to semiconductor devices, and more particularly to a semiconductor device having a bond pad with separate areas for probe needle contact and wire bonding.
2. Description of the Related Art
In integrated circuit manufacturing, wire bonding is a well known method used to connect a semiconductor die having electrical circuitry to a pin on a component package. Within integrated circuit manufacturing it is also a common practice to test the functionality of the semiconductor die before completing component assembly. A “probe test” is a method of testing a semiconductor where a probe contact is commonly used as a mechanical and electrical interface to bond pads on the die.
FIG. 1 illustrates a top view of a bond pad structure 10 formed in a part of an integrated circuit (IC) chip 12 for wire bonding. The bond pad structure 10 includes a bond pad 14, typically rectangular in configuration, which is partially covered by a passivation layer 16. The edges of the bond pad 14 are illustrated by the doted lines in FIG. 1. A pad opening 18 is formed in the passivation layer 16, exposing most of the bond pad 14 for allowing sequential bonding of a bond ball (not shown) thereon. The bond pad 14 electrically contacts an underlying interconnect wiring (not shown). A bond ball (not shown) formed on the bond pad 14 can therefore be connected with a bonding wire (not shown), through a lead (not shown), to the terminals (not shown) on a leadframe or substrate (not shown).
Normally, prior to packaging and formation of the bonding ball on a bond pad 14 exposed by the pad opening 18 in FIG. 1, the IC chip 12 is subjected to parametric testing which utilizes test structures to assess the electrical characteristics and reliability of the devices on the wafer. Probe cards are typically used as an interface between the devices on the chip and automated test equipment. The probe card typically includes a printed circuit board from which multiple probe needles extend, one of the probe needles (illustrated as a probe needle 20 here) is disposed in electrical contact with the device through the bond pad 14, as shown in FIG. 2. The probe needle 20 contacts the bond pad 14 at a probe needle contact area 22 provided on the bond pad 14 in the testing step. Next, a wire bonding area 24 other than that of the probe needle contact area 22 over the bond pad 14 is provided at a place for the sequential wire bonding of a bonding ball in the packaging step. Ideally, the wire bonding area 24 and probe needle contact area 22 of the bond pad 14 are substantially divided by a suppositional line (shown as the dashed line 15 in FIG. 2) and the wire bonding area 24 does not overlap the probe needle contact area 22 since the probe needle 20 typically contacts the bond pad 14 at a typical pressure of about 2-3 grams with a consequently formed scrub mark 32 and hump 34 on pad material the bond pad 14 which cross along the probe needle contact area 22, as shown in FIG. 3 of which a schematic cross section is taken along line 3-3 in FIG. 2.
Nevertheless, with the trend of size reduction in modern deep sub-micron semiconductor technology, bond pad geometry characteristics thereof are also reduced. As the bond pad size is reduced, the ratio of the damage caused by a probe contact to the bond pad area increases. This decreased wire bonding area 24 for the bond ball (not shown) tends to reduce effective bonding of the bond ball to the bond pad 14. Once the wire bonding area 24 overlaps the probe needle contact area 22 on the bond pad 14, the bond ball wire bonded on the bond pad 14 often shows poor adhesion therebetween due to the presence of the probe needle scrub mark 32 and the hump 34 in the surface of the bonding pad 14, thereby causing poor adhesion of the bond ball from the bond pad 14. This increases quality and reliability concerns for bond pads that have been damaged by a probe contact.
Thus, there is a need for the ability to circuit probe test a die without causing unreliable wire bonding connections, and to ensure a robust circuit probe test on die with small bond pads. And in many cases, there is a need to meet the preceding criteria without affecting die size to keep costs down. Accordingly, there is an established need for a new layout for clearly distinguishing regions for test probing and wire bonding on the bonding pad.